1.1. Types of Rib
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True, False and Floating Ribs
The ribs form most of the 'ribcage'. Normally, a human has 12 ribs on each side (so 24 all together). Men and women have the same number of ribs. It is very difficult to feel (palpate) the first rib because the clavicle overlies it. Ribs can be classified in a number of ways: (i) true, false or floating ribs, or (ii) typical and atypical ribs. But what is the anatomical difference between these types of rib?
- Ribs 1 to 7 each have their own costal cartilage that connects them to the sternum. Therefore, they are said to be 'true' ribs.
- Ribs 8 to 10 are 'false' because their costal cartilages merge together and attach to the seventh costal cartilage, which is attached to the sternum. This indirect attachment to the sternum means they are classified as 'false' ribs.
- Ribs 11 and 12 are 'floating' because they are not connected to the sternum, and they have no costal cartilage. In fact, they are deficient anteriorly.
Typical and Atypical Ribs
The typical ribs are 3 - 9. They generally look like the rib shown in Section 1.2. and have all of the labelled features. Each rib articulates with the vertebral body at its level and the vertebral body above (more on this later). The atypical ribs are 1, 2, 10, 11 and 12.
- Rib 1 articulates with T1 only, rib 2 with T1 and T2 (although it is still considered atypical), rib 10 with T10 only, rib 11 with T11 only and rib 12 with T12 only.